Surfboard fin



FIG. 1 is a bottom plan view of a surfboard fin showing my new design;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a front elevational view thereof; and

FIG. 5 is a rear elevational view thereof. 

The ornamental design for a surfboard fin, as shown. 